This invention relates generally to turbines, and, more specifically, to cooling angelwing structures used within gas turbine engines.
At least some known gas turbine engines include an outer rotor/stator cavity through which hot combustion gases pass, and an inner wheelspace that includes components fabricated from materials having a temperature resistance that is lower than temperatures present in the outer rotor/stator cavity. Furthermore, at least some known gas turbine engines include rotor blades. A rotor blade includes a shank, and a connecting structure coupled to the shank, such as a dovetail, used to couple a rotor blade to a rotor wheel. An airfoil is also coupled to the shank. In at least some known rotor blade constructions, the shank includes fore and/or aft walls that extend transversely relative to an axis of rotation of the gas turbine engine. In addition, in at least one known gas turbine engines, at least one cover plate is coupled to a rotor blade and the rotor wheel to facilitate preclusion of gas leakage therebetween.
In at least some known rotor blade constructions, structures commonly referred to as “angelwings,” extend axially fore and/or aft from the shank. In at least some known gas turbine engines, at least two angelwings are provided that extend from an upstream-facing shank wall and/or a downstream-facing shank wall of a rotor blade, such that a first angelwing (hereinafter referred to as a “lower” angelwing) is located radially inwardly of a second angelwing (hereinafter referred to as an “upper” angelwing). When two angelwings are present and facing in the same direction (e.g., extending from a forward face of a shank), the upper or outermost angelwing facilitates prevention of ingestion of hot combustion gases into a buffer cavity defined between the upper and lower angelwings, and both upper and lower angelwings facilitate prevention of ingestion of hot combustion gases into the inner wheelspace. Prevention of hot combustion gas ingestion is desirable to facilitate prevention of damage to inner wheelspace components due to exposure to the hot combustion gases.
In at least some known gas turbine engines, cooling air is channeled under pressure into the inner wheelspace for facilitating prevention of hot combustion gas ingestion into the inner wheelspace. However, the channeling of cooling air into the inner wheelspace may have the effect of reducing engine efficiency. As a result, gas turbine engine designs are evolving such that the amount of cooling air channeled into the inner wheelspace is being reduced. Moreover, in at least some known gas turbine engines, combustion firing temperatures are being increased. Accordingly, providing cooling for gas turbine engine components, in particular components within the inner wheelspace, and preventing ingestion of hot combustion gases, present challenges to designers of gas turbine engines.
In at least some known gas turbine engines, upper surfaces of the angelwings are directly exposed to the hot combustion gases, especially upper angelwings, if both upper and lower angelwings are provided. Accordingly, it is desirable to provide for cooling of the upper surfaces of the angelwings, to facilitate lowering of temperatures of the upper surfaces of the angelwings and to facilitate the prevention of potential creep-related failure of the angelwings. It is further desirable to provide for cooling of upper surfaces of a lower angelwing, if present, to facilitate purging of hot gases from the buffer space, towards facilitating prevention of ingestion of hot combustion gases into the buffer space.